Variable resistance shift rail detent assembly and shift control method employing same

ABSTRACT

A mechanical transmission system ( 10 ) is provided with a detent mechanism ( 156/172, 186/196 ) for applying a selectively variable detent resistance to disengagement of an engaged gear ratio. To provide resistance to shift lever ( 31 ) induced jumpout when no intent to shift is sensed, a greater detent resistance is provided, and to provide improved shift quality upon sensing an intent to shift, a lesser detent resistance is provided. The mechanism also may be utilized to maintain the transmission in neutral.

RELATED APPLICATIONS

This application is a divisional application of reissue application Ser.No. 10/124,934, filed on Apr. 18, 2002.

This application is a continuation of U.S. Ser. No. 08/928,234 nowabandoned filed Sep. 12, 1997, and assigned to EATON CORPORATION, theassignee of this application.

This application is related to U.S. Ser. No. 08/646,225 filed May 6,1996, now U.S. Pat. No. 5,785,543, entitled SHIFT LEVER ASSEMBLY FORMINIMIZING JUMPOUT and Ser. No. 08/902,603 filed Aug. 7, 1997, now U.S.Pat. No. 5,904,635 entitled PARTIALLY AUTOMATED LEVER-SHIFTED MECHANICALTRANSMISSION SYSTEM, both assigned to EATON CORPORATION, the assignee ofthis application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to shift rail detent mechanisms forproviding a selectively variable resistance to axial or rotationalmovement of a shift rail for minimizing the occurrence of jumpout. In aparticular preferred embodiment, the present invention relates to such adetent mechanism for a lever-shifted transmission system having means todetermine a driver intent to initiate or continue a lever shift and,upon sensing such an intent, to cause the detent mechanism to provide adecreased resistance to shift rail movement.

2. Description of the Prior Art

Manually shifted vehicular transmissions of the simple and/or compoundtypes and of the synchronized, blocked and/or non-synchronized types arewell known in the prior art, as may be seen by reference to U.S. Pat.Nos. 5,000,060 and 5,390,561, the disclosures of which are incorporatedherein by reference.

The prior art manually shifted transmissions, especially as utilized forheavy-duty vehicles such as straight trucks and conventional (i.e., notcab-over-engine) tractor/semi-trailers, utilized a manually manipulatedshift lever extending upwardly from a shift tower subassembly mounteddirectly on the transmission housing and interacted with a multiple-railor single shift shaft shifting mechanism of the types shown in U.S. Pat.Nos. 4,455,883; 4,550,627; 4,920,815 and 5,272,931, the disclosures ofwhich are incorporated herein by reference.

While such transmissions are widely used and commercially successful,they are not totally satisfactory, as under certain severe roadconditions, the transmissions may experience shift lever-induced jumpout(i.e., unintended disengagement of a gear ratio). This situation usuallyis associated with transmissions utilized in relatively heavy-dutyvehicles (i e., such as MVMA Class 5 and larger vehicles), which tend tohave relatively long shift levers having relatively large shift knobs,often including master valving for controlling range and/or splittershifts, at the ends thereof.

As is known in the prior art, shift rail detent mechanisms are used tomaintain the shift rails in a fixed position to resist jumpout, such asshift lever-induced jumpout. Examples of such detect mechanisms may beseen by reference to U.S. Pat. Nos. 4,550,627; 4,614,126; 4,920,815;5,000,060 and 5,350,561, the disclosures of which are incorporatedherein by reference. Shift lever detents are also useful to maintain atransmission in neutral when the engine is left running to keep theheater operational. Such mechanisms are not totally satisfactory, as themagnitude of resistance to shift rail movement needed to provide asignificant resistance to jumpout or to resist accidental shifting fromneutral, often objectionably increased the operator effort associatedwith a lever shift.

Partially automated mechanical transmission systems providing automaticassistance, such as automatic engine fuel control, for manuallever-shifted transmissions are known in the prior art, as may be seenby reference to U.S. Pat. Nos. 4,593,580; 5,569,115; 5,571,059;5,573,477 and 5,582,558, the disclosures of which are incorporatedherein by reference, and to co-pending U.S. Ser. Nos. 08/649,829 nowU.S. Pat. No. 5,682,790, 08/649,830 now U.S. Pat. No. 5,735,771,08/649,831, now abandoned, and 08/666,164, all assigned to EATONCORPORATION, the assignee of this application. These systems utilizeautomatic engine fueling controls and/or range and/or splitter shiftactuators, actuated by a driver indication of an intent to shift,allowing an old gear to be disengaged and a new or target gear to beengaged without requiring the driver to manipulate the clutch pedal(required only for vehicle launch and stop) or the throttle pedal.

SUMMARY OF THE INVENTION

In accordance with a preferred embodiment of the present invention, thedrawbacks of the prior art are minimized or overcome by the provision ofa selectively variable detent mechanism for a transmission system havinga means for sensing a driver intent to initiate a lever shift, whichprovides a significant resistance to shift lever-induced jumpout withoutobjectionably increasing the operator effort required to make anintended lever shift.

The foregoing is accomplished by providing a detent mechanism which maybe controlled to a first condition for providing a greater resistance toshift rail movement or to a second condition for providing a lesserresistance to shift rail movement. Upon determining a driver intent toinitiate a lever shift, and preferably until configuring engagement of atarget gear ratio, the detent mechanism is caused to assume the secondcondition wherein detent resistance to shift rail movement (and, thus,to lever shifts) is minimized. When not at the initiation of or during alever shift operation, the detent mechanism is caused to assume thefirst condition wherein a significant detent resistance to shift railmovement (and, thus, to shift lever-induced jumpout) is applied.

Alternatively, operation of the vehicle heater when the transmission isallowed to remain in neutral may cause the detent mechanism to assumethe first condition.

Accordingly, it is an object of the present invention to provide a newand improved shift rail detent mechanism for mechanical transmissionsystems.

This and other objects and advantages of the present invention willbecome apparent from a reading of the following description of thepreferred embodiment taken in connection with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a symbolic representation of a vehicular drive line utilizingthe improved shift rail detent assembly of the present invention.

FIG. 2 is a symbolic illustration of the parameters affecting shiftlever-induced jumpout torque.

FIG. 3 is a symbolic illustration of the parameters affecting detenttorque.

FIGS. 4A-4C are symbolic representations of a heavy-duty, automaticallyassisted, manually shifted transmission system of the typeadvantageously utilizing the present invention.

FIGS. 5 and 6 are schematic illustrations of alternate variableresistance shift rail detent mechanisms.

FIG. 6A is a schematic illustration of the detent mechanism of FIG. 6 ina retracted position.

FIG. 7 illustrates a further alternate embodiment of the presentinvention.

FIG. 8 is a representation, in flow chart format, of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Certain terminology will be used in the following description of thepreferred embodiment for convenience only and will not be limiting. Theterms “upward,” “downward,” “rightward” and “leftward” will designatedirections in the drawings to which reference is made. The terms“forward” and “rearward” will refer, respectively, to the front and rearends of the drive train components as conventionally mounted in thevehicle, being, respectively, to the left and right sides of the variousdrive train components, as illustrated in FIG. 1. The terms “clockwise”and “counterclockwise” will refer to rotational directions as viewedfrom the left side of the vehicle, as shown in FIG. 1. Said terminologyincludes the words above specifically mentioned, derivatives thereof andwords of similar import.

The preferred embodiment of the present invention is illustrated asutilized in a partially automated, lever-shifted mechanical transmissionsystem of the type illustrated in aforementioned U.S. Pat. Nos.4,593,580; 5,569,115 and 5,582,558, and in aforementioned co-pendingU.S. Ser. No. 08/902,603, now U.S. Pat. No. 5,904,635, entitledPARTIALLY AUTOMATED LEVER-SHIFTED MECHANICAL TRANSMISSION SYSTEM.Although the present invention is particularly advantageously utilizedin such systems, its application is not so limited.

A typical vehicular powertrain system 10 advantageously utilizing thepresent invention may be seen by reference to FIG. 1. Powertrain 10 isof the type commonly utilized in heavy-duty vehicles, such as theconventional tractors of tractor/semi-trailer vehicles, and includes anengine, typically a diesel engine 12, a master friction clutch 14contained within a clutch housing, a multiple-speed compoundtransmission 16, and a drive axle assembly 18. The transmission 16includes an output shaft 20 drivingly coupled to a vehicle drive shaft22 by a universal joint 24 for driving the drive axle assembly, as iswell known in the prior art. The transmission 16 is housed within atransmission housing 26 to which is directly mounted the shift tower 28of the shift lever assembly 30.

FIG. 4A illustrates a shift pattern for assisted manual shifting of acombined range-and-splitter-type compound transmission manually shiftedby a manually operated shift lever. Briefly, the shift lever 31 ismovable in the side-to-side or X—X direction to select a particularratio or ratios to be engaged and is movable in the fore and aft or Y—Ydirection to selectively engage and disengage the various ratios. Theshift pattern may include an automatic range shifting feature andautomatically selected and/or implemented splitter shifting, as is knownin the prior art. Manual transmissions utilizing shift mechanisms andshift patterns of this type are well known in the prior art and may beappreciated in greater detail by reference to aforementioned U.S. Pat.Nos. 5,000,060 and 5,390,561.

Typically, the shift lever assembly 30 will include a shift finger orthe like (not shown) extending downwardly into a shifting mechanism 32,such as multiple-rail shift bar housing assembly or a single shift shaftassembly, as is well known in the prior art and as is illustrated inaforementioned U.S. Pat. No. 4,455,883; 4,550,627; 4,920,815 and5,272,931.

In the prior art transmissions of the general type illustrated in FIG. 1but not incorporating the improved shift rail detent assembly of thepresent invention, it is known that annoying shift lever jumpout mayoccur if road conditions are severe. Briefly, shift lever jumpout is theunintended disengagement of the jaw clutches of a manually shiftedtransmission caused by shift lever oscillations in the Y—Y directionabout the Y—Y pivot axis 34 of the shift lever assembly. It is thepurpose of the shift rail detent assembly of the present invention tominimize the occurrences of such shift lever-induced jumpout while notobjectionably increasing shift effort.

In a typical heavy-duty vehicle powertrain, theengine-clutch-transmission assemblage will tend to move, during severeroad conditions, in a vertical manner (as illustrated by arrow 36) andin a pivoting manner about a pivot point or axis 38 (usually located inthe area of the vehicle clutch). As is indicated by arrow 40, an upwardmovement of the assemblage almost always is associated with acounterclockwise rotation of the assemblage around pivot axis 38, while,as indicated by arrow 42, a downward movement of the assemblage almostalways is accompanied by a clockwise rotation of the assemblage aboutthe pivot axis 38.

As understood, shift lever-induced jumpout is forced by the inertialeffects of excessive road-induced vibration in the vehicle drive train.This road-induced shock causes the engine-clutch-transmission assemblageto pitch on its mounts, as shown in FIG. 1. This pitching occurs at thenatural frequency of the engine-clutch-transmission-mount system,usually between about 7 and 10 Hz. This pitching induces relatively highvertical, fore-aft and rotational accelerations on the transmission and,in particular, the shift lever assembly. The shift lever assembly thendevelops an inertial jumpout torque T_(j) about its pivot 34 asdetermined by the sum of the inertial torques thereon, as will bedescribed in greater detail below and as schematically illustrated inFIG. 2. It is noted that the typical rearward offset in transmissionlever tends to increase the jumpout torque.

As will be described in greater detail below and as is schematicallyillustrated in FIG. 3, jumpout torque T_(j) is resisted by the shiftrail or shift shaft detent force multiplied by its moment arm determinedby the distance between the pivot 34 and the shift rail or shaft (i.e.,detent torque T_(o)). Detent force may include the forces required toovercome a detent mechanism, torque lock in the engaged jaw clutches,and frictional forces in the shift mechanism. When the jumpout torqueovercomes the detent torque, shift lever jumpout occurs. This tends tooccur when the drive train has a very low torque, such as vehicle coastconditions, since the friction from so-called torque lock in the drivetrain during driving conditions tends to lock the engaged sliding clutchmembers in engagement and greatly overcomes any jumpout forces imposedthereon.

As the shift lever assembly 30 itself is a dynamic system, it has itsown natural frequency. Unfortunately, this also usually occurs between 7and 10 HZ. This frequency is determined by lever height, lever offset,tower height, and isolator stiffness. If the natural frequency of theengine-clutch-transmission assemblage matches that of the shift leverassembly, propensity for jumpout is greater because the engine-amplifiedinertial forces are amplified further by the lever resonance.

In FIG. 2,

-   -   T_(j)=a_(x)My−a_(y)Mx+I where:        -   T_(j)=Jumpout torque        -   M=Mass of lever        -   I=Moment of inertia of lever        -   a_(x)=Fore/aft acceleration        -   a_(y)=Vertical acceleration        -   =Angular acceleration of lever        -   x=Distance between cg of lever and pivot        -   y=Vertical distance between cg of lever and pivot        -   cg=Center of gravity            while in FIG. 3,    -   T_(o)=F_(x)d where:        -   T_(o)=Detent torque        -   F_(x)=Detent force        -   D=Distance between pivot and rail

FIG. 2 illustrates a mathematical model for calculating the jumpouttorque T_(j) induced in a shift rail by shift lever whip. It is notedthat jumpout torque will be applied in both the counterclockwise andclockwise directions about the shift lever pivot axis 34 but will tendto cause jumpout only in one of these two directions, depending upon thecurrently engaged gear ratio.

One method of minimizing shift lever-induced jumpout is to increase thedetent force F_(x) such that detent torque will almost always exceedjumpout torque. Unfortunately, such an increased detent force, if notrelieved at the time of shifting, will result in objectionably highshift effort.

In a preferred embodiment of the present invention, the forward shiftingof transmission 16, comprising main section 16A coupled to auxiliarysection 16B, is semi-automatically implemented/assisted by the vehicularsemi-automatic transmission system 100, illustrated in FIGS. 4A-4C. Mainsection 16A includes an input shaft 50, which is operatively coupled tothe drive or crank shaft 110 of the vehicle engine 12 by master clutch14, and output shaft 20 of auxiliary section 16B is operatively coupled,commonly by means of a drive shaft to the drive wheels of the vehicle.The auxiliary section 16B is a splitter type, preferably a combinedrange-and-splitter type, as illustrated in U.S. Pat. No. 5,390,561.

The change-gear ratios available from main transmission section 16 aremanually selectable by manually positioning the shift lever 31 accordingto the shift pattern prescribed to engage the particular change gearratio of main section 16A desired. As will be described, manipulation ofthe master clutch (other than when bringing the vehicle to or whenlaunching the vehicle from an at-rest condition) and manualsynchronizing are not requiring. The system includes means to signal anintent to shift into a target ratio and will automatically take actionsto minimize or relieve torque-lock conditions, allowing, if required, aneasier shift into main section neutral from the engaged main sectionratio and further allowing required splitter shifts to be automaticallyand rapidly completed upon a shift into neutral. Upon sensing a neutralcondition, the system will cause engine to rotate at a substantiallysynchronous speed for engaging a target gear ratio.

The system 100 includes sensors 106 for sensing engine rotational speed(ES), 108 for sensing input shaft rotational speed (IS), and 110 forsensing output shaft rotational speed (OS) and providing signalsindicative thereof. As is known, with the clutch 14 engaged and thetransmission engaged in a known gear ratio, ES=IS=OS*GR (see U.S. Pat.No. 4,361,060).

Engine 12 is electronically controlled, including an electroniccontroller 112 communicating over an electronic data link (DL) operatingunder an industry standard protocol such as SAE J-1922, SAE J-1939, ISO11898 or the like. Throttle position (operator demand) is a desirableparameter for selecting shifting points and in other control logic. Aseparate throttle posit on sensor 113 may be provided or throttleposition (THL) may be sensed from the data link. Gross engine torque(T_(EG)) and base engine friction torque (T_(BEF)) also are available onthe data link.

A manual clutch pedal 115 controls the master clutch, and a sensor 114provides a signal (CL) indicative of clutch-engaged or disengagedcondition. The condition of the clutch also may be determined bycomparing engine speed to input shaft speed. A splitter actuator 116 isprovided for operating the splitter section clutch (not shown) inaccordance with compound output signals. The shift lever 31 has a knob118 which contains selector switch 120 by which a driver's intent toshift may be sensed. A preferred embodiment of selector switch 120 maybe seen by reference to FIGS. 4A-4C. Switch 120 includes a body 120A inwhich is pivotably mounted a rocker member 120B. The rocker isspring-based to the centered, non-displaced position illustrated. Theoperator may press surface 120C or 120D of the rocker member to causethe rocker switch to be pivoted in the direction of arrows 120E or 120F,respectively, to select an up- or downshift, respectively. The rockermay be moved in the direction of the arrows and then released to providean “up” or “down” pulse or may be moved to and retained at the “up” or“down” positions to achieve different control results, as will bedescribed in detail below. The rocker may be used to provide multiplepulses to request a skip shift (see U.S. Pat. No. 4,648,290).Alternatively, rocker 120B may be replaced by a toggle,pressure-sensitive surfaces, separate “up” and “down” buttons, or thelike.

A driver's control display unit 124 includes a graphic representation ofthe six-position shift pattern with individually lightable displayelements 126, 128, 130, 132, 134 and 136 representing each of theselectable engagement positions. Preferably, each half of the shiftpattern display elements (i.e., 128A and 128B) will be individuallylightable, allowing the display to inform the driver of the lever andsplitter position for the engaged and/or target ratio. In a preferredembodiment, the engaged ratio is steady lit, while the target ratio isindicated by a flashing light.

The system includes a control unit 146, preferably amicroprocessor-based control unit of the type illustrated in U.S. Pat.Nos. 4,595,986; 4,361,065 and 5,335,566, the disclosures of which areincorporated herein by reference, for receiving input signals 148 andprocessing same according to predetermined logic rules to issue commandoutput signals 150 to system actuators, such as the splitter sectionactuator 116, the engine controller 112 and the display unit 124. Aseparate system controller 146 may be utilized, or the engine ECU 112communicating over an electronic data link may be utilized.

As shown in co-pending patent application U.S. Ser. No. 08/597,304 nowU.S. Pat. No. 5,661,998, the splitter actuator 116 is, preferably, athree-position device, allowing a selectable and maintainable splittersection neutral. Alternatively, a “pseudo” splitter-neutral may beprovided by deenergizing the splitter actuator when the splitter clutch80 is in an intermediate, nonengaged position.

Forward dynamic splitter-only shifts, other than for the more fullyautomatic 9-10 and 10-9 splitter shifts, such as third-to-fourth andfourth-to-third shifts, are automatically implemented upon driverrequest by use of the selector switch 120. By way of example, assuming athree-position splitter actuator, upon sensing that a splitter shift isrequired, by receiving a single “up” signal when engaged in first,third, fifth or seventh, or receiving a single “down” signal whenengaged in second, fourth, sixth or eighth, the ECU 146 will issuecommands to the actuator 116 to bias the actuator toward neutral, and toengine controller 112 to minimize or break torque. This may beaccomplished by causing the engine to dither about a zero flywheeltorque value (see aforementioned U.S. Pat. No. 4,850,236). As soon assplitter neutral is sensed, the engine will be commanded to asubstantially synchronous engine speed for the target gear ratio atcurrent output shaft speed (ES=IS=OS*GR_(T)±E_(RROR)). The engagement istimed, in view of reaction times and shaft speeds and accelerations, tooccur just off synchronous to prevent clutch butting. Automatic splittershifting of this general type is illustrated in aforementioned U.S. Pat.Nos. 4,722,248 and 5,435,212.

The more fully automated 9-10 and 10-9 splitter shifts are implementedin the same manner but are initiated by the ECU, not the selectionswitch 120, in accordance with predetermined shift schedules.

The engaged and neutral (not engaged) conditions of transmission 10 maybe sensed by comparing the input shaft/output shaft rotational speeds toknown gear ratios (ISO/OS=GR_(i=1 tp 10)±Y?) for a period of time.Position sensors may be utilized in lieu of or in addition to inputshaft and output shaft speed logic.

When synchronizing to engage a target ratio, the engine is directed toachieve and remain at a speed about 30 to 100 RPM (preferably about 60RPM) above or below (preferably below) true synchronous speed(ES_(SYNCHRO)=(OS×GR_(T))−45 RPM) to achieve a good quality jaw clutchengagement without butting. To verify engagement of a target ratio, thesystem looks for input shaft speed equaling the product of output shaftspeed and the numerical value of the target ratio, plus or minus about10 to 30 RPM (IS=(OS*GR_(T))±20 RPM) for a period of time, about 100 to400 milliseconds.

The foregoing logic allows transmission engaged and neutral conditionsto be determined on the basis of input and output shaft speeds withoutfalse engagement sensing caused by engine synchronizing for engagementof a target ratio (see co-pending U.S. Ser. No. 08/790,210, now U.S.Pat. No. 5,974,354).

When in an even numbered ratio (i.e., when in the high splitter ratio)and a single upshift is required, a lever upshift (with splitterdownshift) is appropriate and the system, if requested by the driver,will automatically assist in implementing same. Similarly, when in anodd numbered ratio (i.e., when in the low splitter ratio) and a singledownshift is requested, a lever downshift (with splitter upshift) isappropriate and the system, if requested by the driver, willautomatically assist in implementing same. It is noted that in system100, splitter-only shifts may be automatically implemented, while levershifts, with accompanying splitter shifts, require driver initiation andmain section jaw clutch manipulation.

When a combined lever-and-splitter shift is requested, a single pulse ofthe selector in the appropriate direction (as opposed to maintaining therocker 120B in the appropriate displaced position) is taken as simply arequest for an appropriate splitter shift with no automatic assistance,and the splitter will be preselected to shift to the appropriatesplitter position and will do so when the operator manually shifts toneutral or otherwise breaks torque. The driver is then required toengage the appropriate main section ratio without intervention by thecontroller 148. This is substantially identical to the operation of afully manual splitter-type transmission.

If the driver wishes automatic assistance for a combinedlever-and-splitter shift, the rocker member 120B of the selector ismoved to and retained (for at least 50 milliseconds to 1 second) in theappropriate position to request an assisted up- or downshift. Thecontroller 148, upon receiving such a request, will automatically cause(for a period of about 2-5 seconds) the engine to be fueled to ditherabout a zero flywheel torque, thereby reducing or eliminating torquelock conditions and allowing the operator to easily manually shift tomain section neutral (see U.S. Pat. Nos. 4,850,236 and 5,573,477). Thedisplay 124 will steadily light the old gear ratio and flash orotherwise indicate the selected ratio. The ECU 148 will sense forneutral conditions by comparing the ratio of input shaft speed (IS) tooutput shaft speed OS) to known gear ratios. Alternatively or incombination, position sensors may be utilized. The logic will determinethe identity of the target gear ratio GR_(T) as a direct or indirectfunction of current gear ratio GR_(C) and the direction of the requestedshift.

When main section neutral is sensed, the display element correspondingto the disengaged gear ratio will not be lighted, the splitter willautomatically be caused to shift to the appropriate splitter ratio andthe engine will automatically be caused (for a period of about 2-5seconds) to rotate at a substantially synchronous speed (ES=OS*GR_(T))for engaging the target gear ratio (GR_(T)), allowing the operator toeasily manually utilize the shift lever 31 to engage the indicated mainsection ratio. Preferably, the engine will automatically be caused torotate at an offset from or to dither about true synchronous speed (seeU.S. Pat. Nos. 5,508,916 and 5,582,558). Upon sensing engagement of thetarget ratio, the display indicator elements corresponding to the newlyengaged ratio will be steadily lit and engine fuel control will bereturned to the operator. The assisted combined lever and splitter shiftis accomplished without requiring the operator to manipulate the clutchpedal 115 or the throttle pedal 113.

When in or after shifted to the “A” position 136 (i.e., 9/10), the ECU146 will command the fuel controller 112 and splitter operator 116 toautomatically select and implement appropriate 9-10 and 10-9 shifts.Automatic operation within an upper group of ratios is disclosed inaforementioned U.S. Pat. Nos. 4,722,248; 4,850,236 and 4,850,236 and5,498,195. Systems incorporating this feature are sold by EatonCorporation under the “Super 10 Top-2” trademark and by Dana Corporationunder the “Automate-2” trademark.

To shift out of the “A” position, the operator may simply use the clutchpedal 115, throttle pedal 113 and shift lever 57 to perform a fullymanual shift to another ratio. If an assisted lever shifts from “A” toeighth (or a lower ratio) is required, the selector rocker 120B may beretained in the “down” position, which will cause the ECU 146 to commandthe fuel controller 112 and/or splitter actuator 116 to assist the leveror combined lever-and-splitter shift from the engaged “A” ratio (ninthor tenth) to a selected target ratio. Pulses of the selector (and “up”continuing displacement), when in the “A” position, are ignored by theECU.

In transmission systems such as system 100, and in more automatedsystems, the system is provided with a signal indicating, or with ameans for determining, that a shift in the main transmission section 16Ais to be initiated.

According to the present invention, a detent mechanism is provided whichwill provide a variable resistance to shift rail movement from anengaged position. When the system senses a desire to remain in anengaged ratio, the detent provides a detent force which will provide anexceedingly nigh resistance to shift rail movement which will resistshift lever-induced jumpout. As a shift is not occurring, this will haveno adverse effect on shift quality. When an intent to do a lever shiftor a shift in progress is sensed, there is no requirement to preventjumpout and detent resistance or force is minimized to improve shiftquality by reducing shift effort. In more automated systems, this willallow smaller shift actuators to be utilized.

FIG. 5 illustrates one embodiment of variable shift rail detentmechanism. Shift rail 150 (also called a “shift shaft”) has in-gearnotches 152 and 154 which will align with a detect mechanism 156 whenthe transmission is engaged in 1/2, 5/6 or 9/10(A) or in R, 3/4 or 7/8,respectively. A land 158 exists between notches 152 and 154.Alternatively, a small neutral detent (shown in dashed lines) may beutilized.

Shift rail 150 will typically carry one or more shift forks 151 foraxially positioning clutch members 151A in engaged or disengagedposition, as is well known in the prior art.

The detect mechanism includes a plunger 160 having tapered tip 162receivable in the notches and a piston end 164 receivable in a cylinder166. A light compressor spring 168 biases the plunger downwardly intocontact with the notches. The piston and cylinder define a selectivelypressurized and exhausted chamber 170 which is controlled by an actuatorvalve 172 under command from ECU 146.

Upon sensing an intent to shift, chamber 170 is exhausted to minimizethe resistance to axial movement of shaft rail 150. Upon sensing adesire to remain engaged, the chamber 170 is pressurized to maximize thedetent force and, thus, the resistance to axial movement of the shaftrail to resist shift 1(ever-induced jumpout. An onboard source S ofpressurized fluid, such as hydraulic fluid or pressurized air, may beused to pressurize chamber 170.

The detent mechanism of FIGS. 6 and 6A is similar to that illustrated inFIG. 5 in that a shift rail is provided with in-gear notches 178 and 180corresponding generally to notches 152 and 154, respectively. Notches17E8 and 180, however, are not tapered. The notches 178 and 180cooperate with a non-tapered tip 182 of a plunger member 184 of a detentmechanism 186. Plunger member 184 includes a two-sided piston portion188 slidably and sealingly received in a cylinder 190. The pistonportion 188 and cylinder 190 define two separate chambers 192 and 194,which are alternately pressurized and exhausted by control valve 196under command from ECU 146 to cause the plunger to assume an extended orretraced position. The retracted position of the plunger is illustratedin FIG. 6A.

The mechanism in FIG. 6 provides a positive resistance to axial movementof the shift rail 176, as opposed to the resilient resistance to axialmovement of shift rail 150 provided by the mechanism illustrated in FIG.5. Both types of mechanisms, and modifications thereof, are suitable forthe present invention. FIG. 8 illustrates, in a flow chart format, themethod of the present invention.

The embodiment illustrated in FIG. 7 is substantially identical to thatof FIG. 5, except that neutral detent 158A is intended to positivelyretain the shift shaft 150 in the neutral condition and a controlunrelated to dynamic shifting, such as a heater control, provides acontrol input. Such a control is shown in the form of a switch 200. Asis known, in a heavy-duty truck, often it is desirable to leave theengine running in neutral for a long period of time to power the heater,the refrigeration unit or the like. Under such conditions, it is verydesirable to positively lock the transmission in neutral. Plunger 160will cooperate with detent 158A to provide such a positive locking.

Although the present invention has been described with a certain degreeof particularity, it is understood that the description of the preferredembodiment is by way of example only and that numerous changes to formand detail are possible without departing from the spirit and scope ofthe invention as hereinafter claimed.

1. A transmission system (10) comprising a master friction clutch (14)for drivingly coupling an engine (12) to a compound mechanicaltransmission (16) including a main section and an auxiliary section, ashift member (150, 176) for moving a selected positive clutch member(151A) in said main section to a selected one of an engaged or adisengaged position and means (120, 146) independent of operation ofsaid shift member and said master friction clutch for sensing arequirement to move said selected positive clutch member from saidengaged position to said disengaged position and for providing anintent-to-shift signal indicative thereof, said system characterized by:a detent mechanism (156/172, 186/196) for providing a selectivelyvariable resistance to movement of said clutch member from said engagedto said disengaged position, said detent mechanism having a firstcondition for providing a greater resistance to movement of said clutchmember from said engaged to said disengaged position and a secondcondition for applying a lesser resistance to movement of said clutchmember from said engaged to said disengaged position, said detentmechanism assuming said second condition upon sensing saidindent-to-shift signal.
 2. A method for controlling a transmissionsystem comprising a master friction clutch (14) for drivingly couplingan engine ((12) to a compound mechanical transmission (16) including amain section and an auxiliary section, a shift member for moving aselected positive clutch member in said main section to a selected oneof an engaged or a disengaged position, means independent of operationof said shift member and said master friction clutch for sensing arequirement to move said selected positive clutch member from saidengaged position to said disengaged position and for providing anintent-to-shift signal indicative thereof, and a detent mechanism forproviding a selectively variable resistance to movement of said clutchmember from said engaged to said disengaged position, said detentmechanism having a first condition for providing a greater resistance tomovement of said clutch member from said engaged to said disengagedposition and a second condition for applying a lesser resistance tomovement of said clutch member from said engaged to said disengagedposition, said method comprising: in the absence of said intent-to-shiftsignal, causing said detent mechanism to assume said first condition,and upon sensing said intent-to-shift signal, causing said detentmechanism to assume said second condition.
 3. The method of claim 2wherein said means provides a signal indicative of a target gear ratioand said method further comprises causing said detent mechanism toassume said first condition upon sensing engagement of said target gearratio.
 4. A manually shifted change-gear transmission system comprisinga master friction clutch (14) for drivingly coupling an engine (12) to acompound mechanical transmission (16) including a main section and anauxiliary section, a manually operated shift lever for moving a selectedclutch member in said main section to a selected one of an engaged or adisengaged position, said transmission system comprising: meansindependent of operation of said master friction clutch and manualmovement of said shift lever to sense an operator desire to shift saidclutch member from said engaged to said disengaged position and toprovide a signal indicative thereof, and a detent mechanism forproviding a selectively variable resistance to movement of said clutchmember from said engaged to said disengaged position, said detentmechanism having a first condition for providing a greater resistance tomovement of said clutch member from said engaged to said disengagedposition and a second condition for applying a lesser resistance tomovement of said clutch member from said engaged to said disengagedposition, said detent mechanism assuming said second condition uponsensing said signal.
 5. A partially automated transmission systemcomprising a fuel-controlled engine, an engine controller forcontrolling fueling of the engine in accordance with command outputsignals, a compound multiple-speed mechanical transmission having aninput shaft driven through a master friction clutch by the engine, anoutput shaft, a main transmission section shifted by a manual shiftlever and an auxiliary section, an operator selector movable to a firstposition for selection of upshifts to a target ratio and to a secondposition for selection of downshifts to a target ratio, and a controlunit for receiving input signals and processing same according topredetermined logic rules to issue command output signals, said systemcharacterized by: a detent mechanism for providing a selectivelyvariable resistance to movement of said shift lever from a ratio-engagedto a ratio-disengaged position, said detent mechanism having a firstcondition for providing a greater resistance to movement of said shiftlever from said ratio-engaged to said ratio-disengaged position and asecond condition for applying a lesser resistance to movement of saidshift lever from said ratio-engaged to said ratio-disengaged position,and said logic rules being effective to determine, independently ofoperation of said master friction clutch and said shift lever, a driverintent to move said shift lever to said ratio-disengaged position and,upon sensing such intent, causing said detent mechanism to assume saidsecond condition.
 6. The transmission system of claim 5 wherein saidshift lever is operable to cause axial movement of a shift rail, saiddetent mechanism comprising a notch in said rail and a detent plungerbiased with variable force to engage said notch.
 7. The transmissionsystem of claim 6 wherein said notch and said plunger are provided withcomplementary ramped surfaces.
 8. A partially automated transmissionsystem comprising: a fuel-controlled engine, an engine controller forcontrolling fueling of the engine in accordance with command outputsignals, a compound multiple-speed mechanical transmission with a maintransmission section shifted by a manual shift lever in combination withan auxiliary section and having an input shaft driven through a masterfriction clutch by the engine, an output shaft, a first operatorselector movable to a first position for selection of a first mode ofoperation of an accessory otherwise unconnected with the transmissionand said first operator selector movable to a second position forselection of a second mode of operation of said accessory, a secondoperator selector movable to a first position for selection of upshiftsto a target ratio and movable to a second position for selection ofdownshifts to a target ratio, a controller unit for receiving inputsignals and processing same according to predetermined logic rules toissue command output signals, a detent mechanism for providing aselectively variable resistance to movement of said shift lever from aratio-disengaged to a ratio-engaged position, said detent mechanismhaving a first condition for providing a greater resistance to movementof said shift lever from said ratio-disengaged to said ratio-engagedposition and a second condition for applying a lesser resistance tomovement of said shift lever from said ratio-disengaged to saidratio-engaged position, and said logic rules being effective todetermine, dependent on the operator selection of the first mode and thesecond mode of operation of the accessory, a driver intent to maintainsaid shift lever in said ratio-disengaged position and, upon sensingsuch intent, causing said detent mechanism to assume said firstcondition and said logic rules being effective to determine,independently of operation of said master friction clutch and said shiftlever, a driver intent to move said shift lever, wherein saidintent-to-maintain signal is provided only if there is no signal fromthe second operator selector indicating an intent-to-shift.
 9. Atransmission system ( 10 ) comprising: a mechanical transmission for amotor vehicle, the transmission being a compound mechanical transmissionwith a main transmission section shifted by a shift member incombination with an auxiliary section, a master friction clutch fordrivingly coupling an engine to the mechanical transmission, said shiftmember for moving a selected positive clutch member within thetransmission to a selected one of an engaged or a disengaged position,means for sensing a requirement to maintain said selected positiveclutch member in said disengaged position and for providing anintent-to-maintain signal thereof, said intent-to-maintain signal beingdependent on the operation of an accessory otherwise unconnected withthe transmission, a detent mechanism for providing a selectivelyvariable resistance to movement of said clutch member from saiddisengaged to said engaged position, said detent mechanism having afirst condition for providing a greater resistance to movement of saidclutch member from said disengaged to said engaged position and a secondcondition for applying a lesser resistance to movement of said clutchmember from said disengaged to said engaged position, said detentmechanism assuming said first condition upon sensing saidintent-to-maintain signal, a second operator selector movable to a firstposition for selection of upshifts to a target ratio and movable to asecond position for selection of downshifts to a target ratio, and meansindependent of operation of said shift member and said master frictionclutch for sensing a requirement to move said selected positive clutchmember, wherein said intent-to-maintain signal is provided only if thereis no such requirement to move sensed.
 10. A transmission systemcomprising: a compound mechanical transmission for a motor vehicle witha main transmission section in combination with an auxiliary section, amaster friction clutch for drivingly coupling an engine to themechanical transmission, a shift member for moving a selected positionclutch member within the main transmission section to a selected one ofan engaged or disengaged position, means independent of operation ofsaid shift member and said master friction clutch for sensing arequirement to move said selected positive clutch member from saidengaged position to said disengaged position and for providing anintent-to-shift signal indicative thereof, means for sensing arequirement to maintain said selected positive clutch member in saiddisengaged position and for providing an intent-to-maintain signalthereof, said intent-to-maintain signal being dependent on the operationof an accessory otherwise unconnected with the transmission, a detentmechanism for providing a selectively variable resistance to movement ofsaid selected positive clutch member from said engaged to saiddisengaged position, said detent mechanism having a first condition forproviding a greater resistance to movement of said selected positiveclutch member from said engaged to said disengaged position and a secondcondition for applying a lesser resistance to movement of said selectedpositive clutch member from said engaged to said disengaged position,said detent mechanism assuming said second condition upon sensing saidintent-to-shift signal, and said detent mechanism also providing aselectively variable resistance to movement of said selected positiveclutch member from said disengaged to said engaged position, said detentmechanism having a third condition for providing a greater resistance tomovement of said selected positive clutch member from said disengaged tosaid engaged position and a fourth condition for applying a lesserresistance to movement of said selected positive clutch member from saiddisengaged to said engaged position, said detent mechanism assuming saidthird condition upon sensing said intent-to-maintain signal.
 11. Atransmission system as set forth in claim 10 wherein the transmissionsystem also has an operator selector movable to a first position forselection of upshifts to a target ratio and movable to a second positionfor selection of downshifts to a target ratio, further wherein saidintent-to-maintain signal is provided only if no requirement to move issensed.